A printed circuit board (PCB) typically generates heat during operation of circuitry on or in the PCB. High frequency applications often require small element spacing between circuit components on the PCB, which results from the circuitry spacing dictated by the radio frequency lattice spacing. However, this can create difficulties when trying to cool the circuit components.
One conventional thermal management technique utilizes thermal vias to conduct heat into and through a PCB to a heat sink. However, thermal vias can occupy a relatively large amount of space on a PCB. Moreover, increased thicknesses of PCBs often require vias to increase in size, which again increases the amount of space occupied by the vias on a PCB. In addition, the use of thermal vias typically limits scalability and induces thermal gradients. This complicates the PCB design in addition to the difficulties normally experienced trying to meet the requirements of high frequency applications. Note that using thermal vias within a PCB also requires that the heat be removed from either the other side of the PCB opposite to the circuit element side or at the edges.
Other thermal management techniques include immersion cooling and local boiling of a liquid to a vapor state. However, these techniques often require sealing and could potentially affect both radio frequency (RF) characteristics of devices and affect the devices' long-term reliability. Still other thermal management techniques use internal PCB thermal planes (with and without liquid/vapor chambers), but these also occupy large amounts of space in PCBs,